Gonadotrophin-releasing hormone agonists (GnRHa) reduce the size of uterine fibroids and relieve patients of myoma-related symptoms. However, rapid regrowth frequently occurs after the therapy is stopped. We attempted to determine whether GnRHa therapy could lead perimenopausal women carrying symptomatic myomas to the natural onset of the menopause. A retrospective analysis of 145 patients who received GnRHa for 24 weeks demonstrated that after cessation of therapy no menstruation occurred over 25 weeks in women aged over 45 years, with elevated levels of follicle-stimulating hormone (FSH) and luteinising hormone (LH) > 25 mIU/ml. To extend this study, we studied prospectively 21 women, aged 45 years and older who had regular menstruation with symptoms attributed to myomas and elevated days 3 - 5 FSH and days 3 - 5 LH levels ( > 25 mIU/ml). After discontinuation of GnRHa (leuprorelin acetate, 1.88 mg) therapy for 6 months, menstruation occurred in only two of 21 individuals but the remaining 19 cases had no menstrual bleeding. It is suggested from this study that the rise in early follicular phase serum gonadotrophins, in particular FSH > 25 mIU/ml, may precede the natural menopause following (or during) GnRHa therapy in older women. Measuring days 3 - 5 serum FSH concentrations may make it easier to decide on the optimal duration of therapy for symptomatic uterine fibroids in perimenopausal women aged > 45 years.